Is the cash amount I received after completing an accounting task considered a gift or unlawful money, given that this task did not differ from previous ones and that its owner stood out from other companies by having goods taken from him at the same market price?

The purpose of a gift is to win over hearts, as the Prophet (peace be upon him) said: "Give gifts, and you will love one another." Therefore, the Prophet (peace be upon him) was strict regarding accepting gifts from workers and employees. Thus, it is not permissible for you to accept the gift except with the permission of the company owner or the responsible manager.